You can't toss a baguette these days without hitting someone who's talking about the pros and cons of carbs. And yet, with all this carb chatter it's not always easy to figure out exactly which are the good carbs and which are the bad.

Enter the glycemic index (GI) - a reference source that can help indicate which foods are high GI, and therefore most likely to contribute to obesity, type 2 diabetes, and a number of chronic diseases including heart disease. Now a new study reveals that a steady intake of high GI foods may be associated with one of the most common and deadly types of cancer.

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Dangerous load

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The glycemic index is a measurement system developed to help diabetic patients manage their blood glucose levels. In a nutshell: Low GI foods (such as most fruits and vegetables) prompt a slow increase in blood sugar levels, while high GI foods (such as processed baked goods and starchy foods) produce a quick spike in blood sugar levels. A steady intake of high GI foods promotes a gradual insensitivity to insulin - the precursor of type 2 diabetes.

In the e-Alert "Exit Candyland" (3/13/03) I told you about the discovery seventy years ago that cancer cells use glucose (sugar) for growth. All cells have a requirement for glucose, but cancer cells consume as much as 4 to 5 times more glucose than normal, healthy cells. In fact, they're unable to multiply rapidly without it. So the results of this new research from the University of California at Los Angeles (UCLA) are not entirely surprising.

Using data from the Women's Health Study, the UCLA team found 174 cases of colorectal cancer among a group of more than 38,000 women. Researchers estimated the glycemic load (GL) for each subject by analyzing dietary information gathered from food-frequency questionnaires over a period of about eight years. Their conclusion: "Dietary glycemic load was statistically significantly associated with an increased risk of colorectal cancer."

Generally speaking, glycemic load increases when foods that are high on the glycemic index also contain high amounts of carbohydrates.

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Help from down under

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In the e-Alert "Breakfast Special" (9/30/03), I told you about the Daily Dose e-letter in which William Campbell Douglass, M.D., looked at a study of adolescents who ate either instant oatmeal or unprocessed oatmeal for breakfast. The study showed that the group eating instant oatmeal consumed more food later in the day than the unprocessed group. The reason? The higher glycemic index of the instant oatmeal causes it to be digested more rapidly, so hunger returns sooner.

This is one of the worst aspects about foods with a high GI: They actually make you hungrier than foods with a low GI. As a result, you end up eating more. And if the foods you're eating more of are high GI, you're caught in a vicious cycle that can only lead to weight gain and all of the other problems that come tagging along as the pounds increase.

The solution is to become aware of the GI value of the foods you eat. At one time that would have been easier said than done. But a web site operated by the University of Sydney now makes it very easy. The site (glycemicindex.com) provides a GI Database where you can search for the GI and GL of different types of food. The slight drawback for those of us in the U.S. is that the database is sometimes specific about brand names, which are mostly Australian and European. Nevertheless, the database still offers an excellent guide for making low GI dietary choices.

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The next thing

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I believe there's a good chance that all of the current buzz about carbohydrates will soon give way to glycemic index as the hot dietary topic. So if you want to stay ahead of the curve, the next time someone starts talking carbs, tip them off to the index that will help guide them away from the types of carbs that can do the most harm.